The present invention relates to sheet stacking apparatuses that make it possible to stack plural sheets of paper discharged by an image forming apparatus, and to image forming systems in which an image forming apparatus is connected to a sheet stacking apparatus.
In an image forming apparatus, plural stages of sheet discharge trays are provided to separate and discharge sheets of paper on which images have been formed, and sheets are discharged to the discharge tray selected by the user. In Patent Document 1, a proposal has been made, in a paper discharge apparatus provided with plural stages of sheet discharge trays, to provide input means in an image forming apparatus for changing the destination of discharged sheets for each paper discharge tray, thereby making it possible to select the discharge tray to which the sheet is to be discharged even in the middle of printing.
In a high speed printer, very frequently the image forming is done at a high speed and plural sheets of printed paper are discharged in a very short time, and since the capacity of the paper discharge tray or plural stages of paper discharge trays provided in the image forming apparatus to stack sheets of paper becomes insufficient, a sheet stacking apparatus is connected to the image forming apparatus, and the sheets of paper discharged by the image forming apparatus are stored within the racks of the sheet stacking apparatus having a large sheet storing capacity. In addition, in a similar manner, several units of sheet stacking apparatuses are connected to the image forming apparatus thereby not only increasing the capacity of sheet storage but also making it possible to discharge the paper discharged by the image forming apparatus to the selected sheet stacking apparatus.
In Patent Document 2, in a system of connecting plural paper finishers to an image forming apparatus and carrying out specific finishing, technology has been disclosed to avoid the entire system from getting stopped and become unusable when a specific finishing cannot be executed, wherein the finishing is continued by switching over to another paper finisher.
Patent Document 1: Japanese Patent Application Laid Open No. 2004-59268.
Patent Document 2: Japanese Patent Application Laid Open No. Hei 9-301618.